JP2001-304202A describes this type of switching valve.
JP2001-304202A discloses a switching valve including a spool that operates a cylinder by controlling a direction of working oil supplied from a pump, and has an internally formed regeneration passage through which return oil flowing out of a rod side of the cylinder is regenerated to a piston side chamber.
Further, the regeneration passage of the switching valve disclosed in JP2001-304202A includes a radial direction hole capable of communicating with upper and lower working oil supply/discharge grooves positioned at a first end of the spool, an axial direction hole that communicates with the radial direction hole, and a radial direction hole that communicates with the axial direction hole and communicates with upper and lower working oil supply/discharge grooves positioned at a second end of the spool. The return oil flowing out of the rod side of the cylinder is regenerated to the piston side chamber through the radial direction hole in the second end, the axial direction hole, and the radial direction hole in the first end.